Synthesis of oligoesters from oxalic acid and glycerol

A new synthesis for the polycondensation of oxalic acid and glycerol was used. Polycondensation was carried out in the presence of compounds that do not dissolve oxalic acid and glycerol, but form an azeotropic mixture with water below 100°C. Anhydrous oxalic acid and oxalic acid dihydrate was used for the synthesis of oligoesters. The decarboxylation proceeds parallel with polycondensation of oxalic acid and glycerol was investigated. Decarboxylation of carboxyl groups of glycerol monooxalate was found to be accelerated by the arrangement of primary and secondary hydroxyl groups in the glycerol molecule in the 1,2 position.     

Synthesis and characterization of polyesters derived from succinic acid, ethylene glycol and 1,3-propanediol

Poly(ethylene succinate) (PES), poly(trimethylene succinate) (PTS) and their copolyesters with various compositions were synthesized through a direct polycondensation reaction with titanium tetraisopropoxide as the catalyst. The results of intrinsic viscosity and GPC have proven successful in preparing high molecular weight polyesters. The compositions and the sequence distributions of the copolyesters were determined by analyses of ¹H NMR and ¹³C NMR spectra. The sequence distributions of ethylene succinate units and trimethylene succinate (TS) units were found to be random. Their thermal properties were characterized using differential scanning calorimeter and thermal gravimetric analyzer. All of the copolymers exhibit a single glass transition temperature (T_g). There is no significant difference in the thermal stability among these polyesters. Wide angle X-ray diffractograms (WAXD) were obtained for polyesters which can be crystallized isothermally. The results of thermal analysis and the WAXD patterns indicate that the incorporation of TS units into PES significantly inhibits the crystallization behavior of PES. Additionally, the crystal pattern of PTS is quite different from that of PES. Dynamic mechanical properties of moldable polyesters were investigated using a Rheometer operated at 1 Hz. Below T_g, the incorporation of TS units into PES results in the decline of storage modulus. Above T_g, the effect of crystallinity on the storage modulus can be found.     

Water-soluble polyesters from long chain alkylesters of citric acid and poly(ethylene glycol)

Long chain aliphatic alcohols have been used as model compounds to develop a preparative method for a water-soluble material, which could be a carrier for triacontanol, a highly hydrophobic plant growth regulator. New polyesters from long chain aliphatic (C = 12, 18 and 22) mono-1-alkyl citrates and poly(ethylene glycol) were synthesized and characterized by NMR spectroscopy. The polyester containing the triacontyl moiety was obtained from mono-1-triacontyl citrate, which was synthesized from the corresponding alcohol extracted from the Agave fourcroydes. The molecular weight of the polyesters depends on experimental conditions during synthesis such as reaction time, atmosphere, catalyst concentration and temperature. The reaction is second order in the early stage of the polyester synthesis. The reaction rate constant is independent of the length of the aliphatic chain, but it decreases with increasing of the poly(ethylene glycol) employed. Turbidity measurements have been used to study the polyester solubility. Solubility characteristics were found to depend on the of poly(ethylene glycol), the aliphatic-chain length and the value of for the polyester. These preparations could potentially be used to release triacontanol.     

Synthesis and characterization of elastic aliphatic polyesters from sebacic acid, glycol and glycerol

A series of biodegradable polyesters have been prepared from sebacic acid (SA), glycol (Go) and glycerol (Ge) through a two-step process. First the linear prepolymers were prepared from SA and Go, then crosslinked polyesters were obtained from the prepolymer and Ge with different molar ratios. The resulting samples were characterized by Fourier Transform Infrared Spectrum (FTIR), X-ray Photoelectron Spectroscopy (XPS), and Differential Scanning Calorimetry (DSC). Dynamic Contact Angle tests (DCA) and mechanical tests were also investigated. The enzymatic degradation studies were performed at 37 °C in phosphate buffer solution with porcine pancreas lipase. The resultant polyesters were transparent, flexible, insoluble in organic solvents, and the surfaces of the polyesters were hydrophilic. Young’s modulus, tensile strength, glass transition temperature (T_g) and the degree of enzymatic degradation increased with increasing the content of Ge. It was also worth noticing that the surface content of -COOC- groups was a key factor in the enzymatic degradability.     

Synthesis and characterization of ordered polyurethanes from nonsymmetric diisocyanate and ethylene glycol

An ordered polyurethane with a head‐to‐head (H‐H) or tail‐to‐tail (T‐T) content over 95% was prepared by polyaddition reaction of a nonsymmetric monomer, p‐isocyanatobenzyl isocyanate (1) with a symmetric monomer, ethylene glycol (2). The model reactions were studied in detail to demonstrate the feasibility of polymer formation. The polymerization was conducted in THF in the presence of triethylamine (TEA) at 0 °C by slow addition of a half amount of 2 to 1, followed by removing THF and then adding the rest of 2 in DMF at once at 30 °C in the presence of dibutyltin dilaurate (DBTL). The microstructure of the polymer obtained was investigated by ¹³C NMR spectroscopy, and it was found that the polymer had the expected structural regularity. The constitutional regularity of polymers influenced their thermal properties. © 2000 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 38: 2106–2114, 2000     

乙二醇二丙酸酯的合成与溶剂性能研究

以乙二醇二丙酸酯为重点,研究了乙二醇二羧酸酯的合成与性能。用乙二醇和丙酸直接酯化合成乙二醇二丙酸酯,在单因素实验的基础上,用正交法探讨较佳合成条件。采用红外、核磁对产物进行表征。结果表明,n(丙酸)∶n(乙二醇)=2.5∶1,对甲苯磺酸和甲苯分别占反应物总质量的1.0%和10%,反应时间3 h,乙二醇二丙酸酯收率可达87.4%。并结合其他乙二醇二羧酸酯,通过与常见高沸点溶剂性能的比较分析,表明该产物溶解力强,相对环保安全,在涂料、塑料等工业中具有潜在的应用价值。     

Synthesis of polyesters from 1,3-adamantanedicarboxylic acid by low-temperature polycondensation

Conclusions The optimum conditions were found for obtaining the polyester from the acid chloride of 1,3-adamantanedicarboxylic acid and phenolphthalein.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 9, pp. 2098–2100, September, 1972.     

Crystal structures of ethylene glycol and ethylene glycol monohydrate

We have carried out a neutron powder diffraction study of deuterated ethylene glycol (1,2-ethanediol), and deuterated ethylene glycol monohydrate with the D2B high-resolution diffractometer at the Institut Laue-Langevin. Using these data, we have refined the complete structure, including all hydrogen atoms, of the anhydrous phase at 220 K. In addition, we have determined the structure of ethylene glycol monohydrate at 210 K using direct space methods. Anhydrous ethylene glycol crystallizes in space-group P2(1)2(1)2(1) with four formula units in a unit-cell of dimensions a = 5.0553(1) ?, b = 6.9627(1) ?, c = 9.2709(2) ?, and V = 326.319(8) ?(3) [ρ(calc)(deuterated) = 1386.26(3) kg m(-3)] at 220 K. Ethylene glycol monohydrate crystallizes in space-group P2(1)/c with four formula units in a unit-cell of dimensions a = 7.6858(3) ?, b = 7.2201(3) ?, c = 7.7356(4) ?, β = 92.868(3)°, and V = 428.73(2) ?(3) [ρ(calc)(deuterated) = 1365.40(7) kg m(-3)] at 210 K. Both the structures are characterized by the gauche conformation of the ethylene glycol molecule; however, the anhydrous phase contains the tGg' rotamer (or its mirror, g'Gt), whereas the monohydrate contains the gGg' rotamer. In the monohydrate, each water molecule is tetrahedrally coordinated, donating two hydrogen bonds to, and accepting two hydrogen bonds from the hydroxyl groups of neighboring ethylene glycol molecules. There are substantial differences in the degree of weak C-D···O hydrogen bonding between the two crystals, which calls into question the role of these interactions in determining the conformation of the ethylene glycol molecule.     

Synthesis of bicyclic and allyl diesters of oxalic acid

An effective synthesis of mixed, bicyclic, and allyl diesters of oxalic acid. The procedure involves addition of oxalic acid to bicycloheptene hydrocarbons followed by esterification of the resulting monoesters with allyl alcohol. The synthesized diesters are new reactive monomers for the synthesis of high-molecular and other organic compounds.     

Bacterial polyesters grafted with poly(ethylene glycol): Behaviour in aqueous media

An easy method for grafting of poly(3-hydroxyoctanoate-co-3-hydroxyundecenoate) (PHOU) was developed. Oxidation of the pendant double bonds of PHOU into carboxyl groups to yield poly(3-hydroxyoctanoate-co-3-hydroxy-9-carboxydecanoate) (PHOD) and the esterification of the carboxyl side groups with poly(ethylene glycol) (PEG) were carried out in a single reaction solution. The grafting yield is dependent on the molar mass of the PEG graft. The maximum carboxyl group conversion (52%) was obtained with PEG M_n = 350 and decreased with increasing molar mass of PEG (19% for PEG M_n = 2000). Yields were determined by ¹H and ¹³C NMR. Short PEG grafts lowered the glass transition temperature (PHOD-g-PEG 350 −57 °C) compared to PHOD (−19 °C) and PHOU (−39 °C). This effect depends on the COOH conversion and PEG chain length. Grafting enhanced the hydrophilic character of the modified polymers making them soluble in polar solvents, such as alcohols and water/acetone mixtures. PHOD-g-PEG films were more stable towards hydrolytic degradation as PHOD films. No obvious modification of films was observed after more than 200 days at pH 7.2 and 37 °C. The molar mass of the grafted polymers decreased only slightly during this period, while PHOD films were hydrolyzed into soluble fragments.     

Nonswellable and swellable ethylene glycol dimethacrylate-acrylic acid copolymer microspheres

In this study, nonswellable and swellable poly(ethylene glycol dimethacrylate/acrylic acid) copolymer microspheres, in the size range of 50–150 μm, were produced by conventional and modified suspension copolymerizations of the respective monomers, i.e., ethyleneglycol dimethacrylate (EGDMA) and acrylic acid (AA) in aqueous media. Poly(vinyl alcohol) and benzoyl peroxide were used as the stabilizer and the initiator. The diluent, i.e., toluene was included in the polymerization recipe of the modified suspension polymerization. The microspheres were characterized by optical microscopy, FTIR, and FTIR-DRS, and potentiometric titrations. Highly crosslinked, transparent, and nonswellable poly(EGDMA/AA) microspheres were obtained with the conventional suspension polymerization procedure. The modified suspension polymerization provided swellable, opaque, and crosslinked copolymer microspheres. Acrylic acid incorporation into the copolymeric microspheres were significantly higher in the modified procedure, relative to the conventional procedure. © 1996 John Wiley & Sons, Inc.     

Synthesis and characterization of poly(ethylene glycol) derivatives

Five general routes for the preparation of polyoxyethylene [generally referred to as poly(ethylene glycol) or PEG] derivatives are described. These routes are (1) nucleophilic displacements with the alkoxide of PEG, (2) nucleophilic displacement on PEG–tosylate, –mesylate, or –bromide, (3) reductive amination of PEG–aldehyde, (4) reductive amination of PEG–amine, and (5) nucleophilic displacements on the s-triazine derivatives prepared from s-triazine trichloride (cyanuric chloride) and PEG. Eighteen derivatives are prepared and potential applications to catalysis, cell purifications, and other areas are discussed briefly.     

Thermal transformations of urea in ethylene glycol: II. Reaction of isocyanic acid with ethylene glycol associates

The reaction of isocyanic acid with ethylene glycol associates was studied by the B3LYP/6–311++G(df,p) quantum chemical method. The reaction mechanism includes formation of pre- and post-reaction complexes and cyclic asymmetric late transition states. The energy barrier decreases with increase in the degree of association of ethylene glycol.     

Synthesis and characterization of polyesters derived from sebacic acid,hexanediol, and hydroquinone

Oils and fats derived from animals and plants provide a good renewable source for polymer precursors. In this investigation, fatty acids derived from plant oils and diols were used as monomers to produce polyesters by melt polycondensation. Sebacic acid, hexanediol, and hydroquinone were used as precursors in the polymer synthesis. The polymers were characterized by gel permeation chromatography, Fourier transform infrared spectroscopy, three-bending point flexural test, X-ray diffraction, tensile testing, and contact angle. The resulting polyesters were blended with epoxies to create materials with an increased elongation at break without affecting other mechanical properties.     

Synthesis of polyesters from active diesters

Ester-exchange and polycondensation reactions of active diesters such as diphenyl, dithiophenyl, or dipyridinyl esters of adipic or terephthalic acids with glycols were carried out in order to investigate the reactivity of these active diesters toward nucleophilic replacement. Catalysts such as potassium carbonate were required for the esterexchange of these active diesters. Comparison of the reactivity of these active diesters with that of ordinary diesters in the presence of potassium carbonate as a catalyst indicates the rates or the equilibrium constants of the exchange reactions of these active diesters were much larger than those of ordinary diesters, indicating that polyesterification reactions favorably occur. Polyesters were obtained in good yield either by solution or bulk methods in mild conditions.     

Copolymer of tetraethylenepentamine and ethylene glycol diacrylate: Synthesis and degradation

A degradable polycation with high density of discrete charge was synthesized from tetraethylenepentamine (TEPA) and ethylene glycol diacrylate (EGDA) based on Michael addition and amidation. The cationic polymer synthesized here was denoted as PTE. Polymerization was monitored by ¹H NMR spectroscopy. According to ¹H NMR spectra, Michael addition proceeded more rapidly than amidation. After 6 h, there were no double bonds left, while amidation existed throughout the polymerization. In addition, when PTE was synthesized in chloroform and dichloromethane, respectively, there were some structural differences as shown by ¹H NMR spectroscopy. The degradation laws of PTE in aqueous solution were studied by ¹H NMR and viscosity measurements. When PTE was dissolved in deionized water, degradation proceeded in high velocity. However, in NaH₂PO₄ aqueous solution, degradation was slowered. Degradation at 37 °C proceeded obviously more rapidly than that at 25 °C. A certain degree of amidation facilitated the reduction of degradation velocity. The effect of concentration on degradation was not obvious. Interestingly, PTE synthesized in CHCl₃ was degraded more rapidly than that in CH₂Cl₂.     

Sulphur-containing polymers: Synthesis and thermal properties of novel polyesters based on dithiotriethylene glycol

Poly(dithiotriethylene terephthalate) (PSSTET), poly(dithiotriethylene adipate) (PSSTEA), poly(triethylene terephthalate) (PTET) and poly(triethylene adipate) (PTEA), these two last for comparison, were synthesized and characterized in terms of chemical structure and molecular weight. The thermal behaviour was examined by thermogravimetric analysis and differential scanning calorimetry. All the polymers showed a good thermal stability, even though lower for the sulphur-containing polyesters. At room temperature they appeared as semicrystalline materials, except PTEA, which was an oil; the effect of substitution of ether oxygen atoms with sulphur ones was found to be a lowering in the T_g value, an increment of the melting temperature and an increase of the crystallization rate. The results were explained as due to the presence of flexible C-S-C bonds in the polymeric chain. Lastly, the absence of a rigid-amorphous phase was evidenced in PSSTET and PTET.